Lead Directing Double - The conventional use of a double requesting a Club lead over
opponents' Notrump contract or a Diamond lead if opponents' made an
undoubled 2C Stayman call. When opponents begin and conclude
the auction in Notrump, the opening leader normally seeks a major suit lead.
The Fisher Double is intended to provide the opening leader specific lead
instruction to beat the contract where a normal major lead would fail to set
Fisher Double has some merit, a more robust use of the double in this
situation is the Lightener Game
Double asking partner to deduce the best lead based on partner's
long running suit, i.e., opening leader's short suit.